oslectureset1spr20.pptx

Principles of Operating Systems -
Lecture 1 1
ICS 143A - Principles of
Operating Systems
(Spring 2020)
Lecture 1 - Introduction and Overview
MWF 11:00- 11:50 a.m.
Prof. Nalini Venkatasubramanian
( nalini@uci.edu )
[lecture slides contains some content adapted from :
Silberschatz textbook authors, John Kubiatowicz (Berkeley)
Anderson textbook, John Ousterhout(Stanford), Prof. Ardalan
Sani, )
]

Lecture 1 2
ICS 143A Spring 2020 Staff
Instructor:
Prof. Nalini Venkatasubramanian (Venkat)
( nalini@uci.edu )
Teaching Assistants:
Biswadeep Maity (Deep) (maityb@uci.edu)
Saehanseul Yi (Hans) (saehansy@uci.edu)
Andrew Chio (achio@uci.edu)

Lecture 1 3
Course logistics and details
● Course Web page -
● http://www.ics.uci.edu/~ics143
● All new announcements and updates will be on class webpage
● Lectures – MWF 11:00 – 11:50, on zoom
● Zoom link: https://uci.zoom.us/j/568633190
● Discussions
● Tuesday 5pm - 6pm; 7pm- 8pm
● Zoom Link:
● 5 - 6 pm session: https://uci.zoom.us/j/556715006
● 7- 8 pm session: https://uci.zoom.us/j/563851913

● ICS 143 Textbook
● Operating System Concepts – 9th Edition, Silberschatz, Galvin and Gagne, Addison-Wesley
Inc (Eighth, Seventh,Sixth and Fifth editions, and Java Versions are fine ).
● Other Suggested Books
● Modern Operating Systems, by Tanenbaum
● Lubomir Bic, online book -- zybooks
● https://www.zybooks.com/catalog/operating-systems/
● Operating Systems: Principles and Practice, by T. Anderson and M. Dahlin
(second edition)
● Piazza for group discussions (https://piazza.com/uci/spring2020/cs143)
● Q/A, Student discussions, monitored by ICS143A staff
● Avoid duplicate posts, Use clear, descriptive titles
● Please be respectful to each other
4

Lecture 1 5
● Homeworks and Assignments
● 4 written homeworks in the quarter
● 1 programming assignment (knowledge of C, C++ or Java
required).
● Handed out at midterm; submit during Finals Week
● Multistep assignment – don’t start in last week of classes!!!
● Late homeworks will not be accepted.
● All submissions will be made using Gradescope for the course
● Tests
● Midterm - tentatively Wednesday, Week 6
● Detailed format and tools to be used -- TBD
● Final Exam - as per UCI course catalog
● June 9th (1:30 - 3:30 pm)
● Detailed format and tools to be used -- TBD

Lecture 1 6
ICS 143 Grading Policy
● Homeworks - 40% (10% each)
● Programming Assignment - 10%
● released Week 6
● Midterm - 20% of the final grade
● Tentatively Wed, Week 6 during lecture
● Final exam - 30% of the final grade
● Per UCI course catalog, Jun 9th (1:30 - 3:30 pm)
● 3 In-class micro-quizzes (not graded, except in case of borderline grades)
Final assignment of grades will be based on a curve.

Lecture 1 7
Lecture Schedule
● Week 1:
• Introduction to Operating Systems, Computer System
Structures, Operating System Structures
● Week 2 : Process Management
• Processes and Threads, CPU Scheduling
● Week 3: Process Management
• CPU Scheduling, Process Synchronization
• Process Synchronization
• Process Synchronization, Deadlocks

Lecture 1 8
Course Schedule
● Week 6 – Deadlocks, Storage Management
• Deadlocks, Midterm revision, exam
● Week 7 - Storage Management
• Memory Management, Paging, Segmentation
● Week 8 – Storage Management
• Virtual Memory
● Week 9 - FileSystems
• Virtual Memory, FileSystems Interface and Implementation
● Week 10 – I/O Subsystems
• Filesystems, I/O, course revision and summary.

Other Logistics
● Office Hours
● Prof. V - Tuesdays (11 am - 12 noon)
● TA office hours – Mon, Wed. Thurs (to be announced on
website)
● Slides
● Available as draft before lecture, minor modifications likely
● If there are missed lectures
● Alternatives will be arranged
Lecture 1 9

Lecture 1 10
Introduction
● What is an operating system?
● Operating Systems History
● Simple Batch Systems
● Multiprogrammed Batch Systems
● Time-sharing Systems
● Personal Computer Systems
● Parallel and Distributed Systems
● Real-time Systems

Lecture 1 11
What is an Operating System?
● An OS is a program that acts an intermediary
between the user of a computer and computer
hardware.
● Major cost of general purpose computing is
software.
● OS simplifies and manages the complexity of running
application programs efficiently.

Lecture 1 12
Computer System
Components
● Hardware
● Provides basic computing resources (CPU, memory, I/O devices).
● Operating System
● Controls and coordinates the use of hardware among application programs.
● Application Programs
● Solve computing problems of users (compilers, database systems, video games,
business programs such as banking software).
● Users
● People, machines, other computers

Lecture 1 13
Abstract View of System
System and Application Programs
Operating System
Computer
Hardware
User
1 User
2
User
3
User
n
compiler assembler Text editor Database
system
...

Lecture 1 14
Operating System Views
● Resource allocator
● to allocate resources (software and hardware) of the
computer system and manage them efficiently.
● Control program
● Controls execution of user programs and operation of I/O
devices.
● Kernel
● The program that executes forever (everything else is an
application with respect to the kernel).

Operating system roles
• Referee
• Resource allocation among users, applications
• Isolation of different users, applications from each other
• Communication between users, applications
• Illusionist
• Each application appears to have the entire machine to itself
• Infinite number of processors, (near) infinite amount of
memory, reliable storage, reliable network transport
• Glue
• Libraries, user interface widgets, …
• Reduces cost of developing software
15

Example: file systems
• Referee
• Prevent users from accessing each other’s files without
permission
• Illusionist
• Files can grow (nearly) arbitrarily large
• Files persist even when the machine crashes in the middle of a
save
• Glue
• Named directories, printf, …
16

Lecture 1 17
Goals of an Operating System
● Simplify the execution of user programs and
make solving user problems easier.
● Use computer hardware efficiently.
● Allow sharing of hardware and software resources.
● Make application software portable and versatile.
● Provide isolation, security and protection among
user programs.
● Improve overall system reliability
● error confinement, fault tolerance, reconfiguration.

Lecture 1 18
Why should I study Operating
Systems?
● Need to understand interaction between the hardware
and applications
● New applications, new hardware..
● Inherent aspect of society today
● Need to understand basic principles in the design of
computer systems
● efficient resource management, security, flexibility
● Increasing need for specialized operating systems
● e.g. embedded operating systems for devices - cell phones,
sensors and controllers
● real-time operating systems - aircraft control, multimedia
services

Computer System Architecture
(traditional)

Systems Today
Lecture 1 20

Hardware Complexity
Increases
Lecture 1 22
Moore’s Law: 2X
transistors/Chip Every 1.5 years
Moore’s
Law
From Berkeley OS course
From Hennessy and Patterson, Computer Architecture: A Quantitative
Approach, 4th edition, Sept. 15, 2006
Intel Multicore Chipsets

OS needs to keep pace with
hardware improvements
23
$/

Software Complexity Increases
Lecture 1 24
From MIT’s 6.033 course

People-to-Computer Ratio Over
Time
From David Culler (Berkeley)

Lecture 1 26
Operating System Spectrum
● Monitors and Small Kernels
● special purpose and embedded systems, real-time systems
● Batch and multiprogramming
● Timesharing
● workstations, servers, minicomputers, timeframes
● Transaction systems
● Personal Computing Systems
● Mobile Platforms, devices (of all sizes)

Lecture 1 27
Early Systems - Bare Machine
(1950s)
● Structure
● Large machines run from console
● Single user system
• Programmer/User as operator
● Paper tape or punched cards
● Early software
● Assemblers, compilers, linkers, loaders, device drivers, libraries of
common subroutines.
● Secure execution
● Inefficient use of expensive resources
● Low CPU utilization, high setup time.
From John Ousterhout slides
Hardware – expensive ; Human – cheap

Simple Batch Systems
(1960’s)
● Reduce setup time by batching jobs with similar requirements.
● Add a card reader, Hire an operator
● User is NOT the operator
● Automatic job sequencing
● Forms a rudimentary OS.
● Resident Monitor
● Holds initial control, control transfers to job and then back to monitor.
● Problem
● Need to distinguish job from job and data from program.
Lecture 1 28

Lecture 1 29
Supervisor/Operator Control
● Secure monitor that controls job processing
● Special cards indicate what to do.
● User program prevented from performing I/O
● Separate user from computer
● User submits card deck
● cards put on tape
● tape processed by operator
● output written to tape
● tape printed on printer
● Problems
● Long turnaround time - up to 2 DAYS!!!
● Low CPU utilization
• I/O and CPU could not overlap; slow mechanical devices.
IBM 7094

Lecture 1 30
Batch Systems - Issues
● Solutions to speed up I/O:
● Offline Processing
● load jobs into memory from tapes, card reading and line printing are done
offline.
● Spooling
● Use disk (random access device) as large storage for reading as many input
files as possible and storing output files until output devices are ready to
accept them.
● Allows overlap - I/O of one job with computation of another.
● Introduces notion of a job pool that allows OS choose next job to run so as
to increase CPU utilization.

Lecture 1 31
Speeding up I/O

Lecture 1 32
Batch Systems - I/O
completion
● How do we know that I/O is complete?
● Polling:
● Device sets a flag when it is busy.
● Program tests the flag in a loop waiting for completion of
I/O.
● Interrupts:
● On completion of I/O, device forces CPU to jump to a specific
instruction address that contains the interrupt service
routine.
● After the interrupt has been processed, CPU returns to code
it was executing prior to servicing the interrupt.

Lecture 1 33
Multiprogramming
● Use interrupts to run multiple programs
simultaneously
● When a program performs I/O, instead of polling, execute
another program till interrupt is received.
● Requires secure memory, I/O for each program.
● Requires intervention if program loops
indefinitely.
● Requires CPU scheduling to choose the next job
to run.

Lecture 1 34
Timesharing
● Programs queued for execution in FIFO order.
● Like multiprogramming, but timer device
interrupts after a quantum (timeslice).
● Interrupted program is returned to end of FIFO
● Next program is taken from head of FIFO
● Control card interpreter replaced by command
language interpreter.
Hardware – getting cheaper; Human – getting expensive

Lecture 1 35
Timesharing (cont.)
● Interactive (action/response)
● when OS finishes execution of one command, it seeks
the next control statement from user.
● File systems
● online filesystem is required for users to access data and
code.
● Virtual memory
● Job is swapped in and out of memory to disk.

Lecture 1 36
Personal Computing Systems
● Single user systems, portable.
● I/O devices - keyboards, mice, display screens, small
printers.
● Laptops and palmtops, Smart cards, Wireless devices.
● Single user systems may not need advanced CPU
utilization or protection features.
● Advantages:
● user convenience, responsiveness, ubiquitous
Hardware – cheap ; Human – expensive

Lecture 1 37
Parallel Systems
● Multiprocessor systems with more than one CPU
in close communication.
● Improved Throughput, economical, increased
reliability.
● Kinds:
• Vector and pipelined
• Symmetric and asymmetric multiprocessing
• Distributed memory vs. shared memory
● Programming models:
• Tightly coupled vs. loosely coupled ,message-based vs. shared
variable

Parallel Computing Systems
Lecture 1 38
Climate modeling,
earthquake
simulations, genome
analysis, protein
folding, nuclear fusion
research, …..
ILLIAC 2 (UIllinois)
Connection Machine (MIT)
IBM Blue Gene
Tianhe-1(China)
K-computer(Japan)

Lecture 1 39
Distributed Systems
● Distribute computation among many processors.
● Loosely coupled -
• no shared memory, various communication lines
● client/server architectures
● Advantages:
• resource sharing
• computation speed-up
• reliability
• communication - e.g. email
● Applications - digital libraries, digital multimedia
Hardware – very cheap ; Human – very expensive

Distributed Computing Systems
Lecture 1 40
Globus Grid Computing Toolkit Cloud Computing Offerings
PlanetLab Gnutella P2P Network

Lecture 1 41
Real-time systems
● Correct system function depends on timeliness
● Feedback/control loops
● Sensors and actuators
● Hard real-time systems -
● Failure if response time too long.
● Secondary storage is limited
● Soft real-time systems -
● Less accurate if response time is too long.
● Useful in applications such as multimedia, virtual reality.

A personal computer today
● Super AMOLED display
● Capacitive touchscreen
(multitouch)
● Audio (speaker, microphone)
● Vibration
● S pen
● 4G LTE
● NFC
● WiFi
● Bluetooth
● Infrared
● 64 GB internal storage (extended
by microSD)
● Adreno 330 GPU
● Hexagon DSP
● Multimedia processor
● 13 MP front camera
● 2 MP back camera
● Accelerometer
● Gyroscope
● Proximity sensor
● Compass
● Barometer
● Temperature sensor
● Humidity sensor
● Gesture Sensor
● GPS
42
interaction

(multitouch)
● Vibration
● S pen
● 4G LTE
● NFC
● WiFi
● Bluetooth
● Infrared
by microSD)
● Adreno 330 GPU
● Hexagon DSP
● Accelerometer
● Gyroscope
● Compass
● Barometer
● Humidity sensor
● Gesture Sensor
● GPS
43
sensing

(multitouch)
● Vibration
● S pen
● 4G LTE
● NFC
● WiFi
● Bluetooth
● Infrared
by microSD)
● Adreno 330 GPU
● Hexagon DSP
● Accelerometer
● Gyroscope
● Compass
● Barometer
● Humidity sensor
● Gesture Sensor
● GPS
44
connectivity

(multitouch)
● Vibration
● S pen
● 4G LTE
● NFC
● WiFi
● Bluetooth
● Infrared
by microSD)
● Adreno 330 GPU
● Hexagon DSP
● Accelerometer
● Gyroscope
● Compass
● Barometer
● Humidity sensor
● Gesture Sensor
● GPS
45
acceleration

Operating systems are
everywhere
46

Operating systems are
everywhere
47

Lecture 1 49
Summary of lecture
● What is an operating system?
● Early Operating Systems
● Simple Batch Systems
● Multiprogrammed Batch Systems
● Time-sharing Systems
● Personal Computer Systems
● Parallel and Distributed Systems
● Real-time Systems

Computer System & OS Structures
• Computer System Organization
• Operational Flow and hardware protection
• System call and OS services
• Storage architecture
• OS organization
• OS tasks
• Virtual Machines
50

Computer System Organization
51

Fetch
Exec
R0
…
R31
F0
…
F30
PC
…
Data1
Data0
Inst237
Inst236
…
Inst5
Inst4
Inst3
Inst2
Inst1
Inst0
Addr 0
Addr 232-1
CPU execution
• Execution sequence:
• Fetch Instruction at PC
• Decode
• Execute (possibly using registers)
• Write results to registers/mem
• PC = Next Instruction(PC)
• Repeat
PC
PC
PC
PC
From Berkeley OS course
52

Computer System Organization
53
I/O devices

I/O devices
• I/O devices and the CPU execute concurrently.
• Each device controller is in charge of a particular
device type
• Each device controller has a local buffer. I/O is from the
device to local buffer of controller
• CPU moves data from/to main memory to/from the
local buffers
54

Interrupts
• Interrupt transfers control to the
interrupt service routine
• Interrupt Service Routine: Segments of
code that determine action to be taken for
interrupt.
• Determining the type of interrupt
• Polling: same interrupt handler called for
all interrupts, which then polls all devices
to figure out the reason for the interrupt
• Interrupt Vector Table: different interrupt
handlers will be executed for different
interrupts
55

Interrupt handling
• OS preserves the state of the CPU
• stores registers and the program counter (address of
interrupted instruction).
• What happens to a new interrupt when the CPU
is handling one interrupt?
• Incoming interrupts can be disabled while another interrupt is
being processed. In this case, incoming interrupts may be lost or
may be buffered until they can be delivered.
• Incoming interrupts can be masked (i.e., ignored) by software.
• Incoming interrupts are delivered, i.e., nested interrupts.
56

Direct Memory Access (DMA)
Memory
CPU
I/O devices
I/O instructions
57
• Typically used for I/O devices
with a lot of data to transfer (in
order to reduce load on CPU).
• Device controller transfers
blocks of data from buffer
storage directly to main
memory without CPU
intervention.
• Device controller interrupts
CPU on completion of I/O
• Only one interrupt is generated
per block, rather than one per
byte (or word).

Process Abstraction
• Process: an instance of a program, running
with limited rights
59

Process Abstraction and rights
• Process: an instance of a program, running
with limited rights
• Address space: set of rights of a process
• Memory that the process can access
• Other permissions the process has (e.g., which
system calls it can make, what files it can access)
60

Hardware Protection
• CPU Protection:
• Dual Mode Operation
• Timer interrupts
• Memory Protection
• I/O Protection
61

How to limit process rights?
62

Should a process be able to
execute any instructions?
63

Should a process be able to
execute any instructions?
● No
● Can alter system configuration
● Can access unauthorized memory
● Can access unauthorized I/O
● etc.
● How to prevent?
64

Dual-mode operation
• Provide hardware support to differentiate between at
least two modes of operation:
1. User mode -- execution done on behalf of a user.
2. Kernel mode (monitor/supervisor/system mode) --
execution done on behalf of operating system.
• “Privileged” instructions are only executable in the
kernel mode
• Executing privileged instructions in the user mode
“traps” into the kernel mode
●Trap is a software generated interrupt caused either by
an error or a user request
65

Dual-mode operation(cont.)
• Mode bit added to computer
hardware to indicate the current
mode: kernel(0) or user(1).
• When an interrupt or trap
occurs, hardware switches to
kernel mode.
User
Kernel
Set
user
mode
Interrupt/
fault
66

CPU Protection
• How to prevent a process from executing
indefinitely?
67

CPU Protection
• Timer - interrupts computer after specified period to
ensure that OS maintains control.
• Timer is decremented every clock tick.
• When timer reaches a value of 0, an interrupt occurs.
• Timer is commonly used to implement time
sharing.
• Timer is also used to compute the current time.
• Programming the timer can only be done in the
kernel since it requires privileged instructions.
68

How to isolate memory
access?
69

Process
Address
Space
Process address space
• Address space ⇒ the set of accessible
addresses + state associated with them:
• For a 32-bit processor there are 232 = 4 billion
addresses
• What happens when you read or write to an
address?
• Perhaps Nothing
• Perhaps acts like regular memory
• Perhaps ignores writes
• Perhaps causes I/O operation
• (Memory-mapped I/O)
• Perhaps causes exception (fault)
70
(code)

Providing the Illusion of Separate Address Spaces
Proc 1
Virtual
Address
Space 1
Proc 2
Virtual
Address
Space 2
Code
Data
Heap
Stack
Code
Data
Heap
Stack
Data 2
Stack 1
Heap 1
kernel heap &
Stacks
Code 1
Stack 2
Data 1
Heap 2
Code 2
kernel code
kernel data
Translation Map 1 Translation Map 2
Physical Address Space 72

Address translation and memory
protection
Processor Translation
Physical
Memory
Data
Data
Valid
Invalid
Raise
Exception
Physical
address
73
Virtual
address

Memory Protection
• When a process is running, only memory in that process
address space must be accessible.
• When executing in kernel mode, the kernel has
unrestricted access to all memory.
• Must provide memory protection at least for the
interrupt vector and the interrupt service routines.
74

Memory Protection: base and limit
• To provide memory protection, add
two registers that determine the
range of legal addresses a program
may address.
• Base Register - holds smallest
legal physical memory address.
• Limit register - contains the size
of the range.
• Memory outside the defined range
is protected.
• Sometimes called Base and
Bounds method
0
300040
420940
1024000
300040
120900
Base register
Limit register
75

Hardware Address Protection
The load instructions for the base and limit
registers are privileged instructions.
76

Virtual Address translation using the
Base and Bounds method
77
The load instructions for the base and limit
registers are privileged instructions.

I/O Protection
• All I/O instructions are privileged instructions.
• Must ensure that a user program could never gain
control of the computer in kernel mode, e.g., a user
program must not be able to store a new address
in the interrupt vector.
78

Question
• Given the I/O instructions are privileged, how do
users perform I/O?
79

Question
• Given the I/O instructions are privileged, how do
users perform I/O?
• Via system calls - the method used by a process to
request action by the operating system.
80

System Calls
• User code can issue a syscall, which causes a trap
• Kernel handles the syscall
81

System Calls
• Interface between applications
and the OS.
• Application uses an
assembly instruction to trap into
the kernel
• Some higher level languages
provide wrappers for system
calls (e.g., C)
• System calls pass parameters
between an and OS via registers
or memory, memory tables or
stack.
• Linux has about 300 system
calls
• read(), write(), open(), close(),
fork(), exec(), ioctl(),…..
82

System services or system
programs
• Convenient environment for program development
and execution.
• Command Interpreter (i.e., shell) - parses/executes other
system programs
• Window management
• System libraries, e.g., libc
83

Command Interpreter System
• Commands that are given to the operating system
via command statements that execute
• Process creation and deletion, I/O handling, secondary
storage management, main memory Management, file
system access, protection, networking, etc.
• Obtains the next command and executes it.
• Programs that read and interpret control
statements also called -
• Command-line interpreter, shell (in UNIX)
84

Storage Structure
• Main memory - only large storage media that the
CPU can access directly.
• Secondary storage - has large nonvolatile storage
capacity.
• Magnetic disks - rigid metal or glass platters covered with
magnetic recording material.
• Disk surface is logically divided into tracks, subdivided into
sectors.
• Disk controller determines logical interaction between device
and computer.
85

Storage Hierarchy
• Storage systems are organized in a hierarchy
based on
• Speed
• Cost
• Volatility
• Caching - process of copying information into
faster storage system; main memory can be
viewed as fast cache for secondary storage.
86

OS Task: Process Management
• Process - fundamental concept in OS
• Process is an instance of a program in execution.
• Process needs resources - CPU time, memory, files/data
and I/O devices.
• OS is responsible for the following process
management activities.
• Process creation and deletion
• Process suspension and resumption
• Process synchronization and interprocess communication
• Process interactions - deadlock detection, avoidance and
correction
88

OS Task: Memory Management
• Main Memory is an array of addressable words or
bytes that is quickly accessible.
• Main Memory is volatile.
• OS is responsible for:
• Allocate and deallocate memory to processes.
• Managing multiple processes within memory - keep track of which
parts of memory are used by which processes. Manage the
sharing of memory between processes.
• Determining which processes to load when memory becomes
available.
89

OS Task: Secondary Storage and I/O
Management
• Since primary storage (i.e., main memory) is
expensive and volatile, secondary storage is
required for backup.
• Disk is the primary form of secondary storage.
• OS performs storage allocation, free-space management,
etc. and disk scheduling.
• I/O system in the OS consists of
• Device driver interface that abstracts device details
• Drivers for specific hardware devices
90

OS Task: File System Management
• File is a collection of related information -
represents programs and data.
• OS is responsible for
• File creation and deletion
• Directory creation and deletion
• Supporting primitives for file/directory manipulation.
• Mapping files to disks (secondary storage).
• Backup files on archival media (tapes).
91

OS Task: Protection and Security
• Protection mechanisms control access of processes to user
and system resources.
• Protection mechanisms must:
• Distinguish between authorized and unauthorized use.
• Specify access controls to be imposed on use.
• Provide mechanisms for enforcement of access control.
• Security mechanisms provide trust in system and privacy
• authentication, certification, encryption etc.
92

Operating Systems: How are they
organized?
• Simple
• Only one or two levels of code
• Layered
• Lower levels independent of upper levels
• Modular
• Core kernel with Dynamically loadable modules
• Microkernel
• OS built from many user-level processes
93

OS Structure - Simple Approach
• MS-DOS - provides a lot of functionality in little
space.
• Not divided into modules, Interfaces and levels of
functionality are not well separated
94

Original UNIX System Structure
• Limited structuring, has 2 separable parts
• Systems programs
• Kernel
• everything below system call interface and above physical hardware.
• Filesystem, CPU scheduling, memory management
95

Layered OS Structure
• OS divided into number of
layers - bottom layer is
hardware, highest layer is
the user interface.
• Each layer uses functions
and services of only lower-
level layers.
• THE Operating System and
Linux Kernel has successive
layers of abstraction.
96

Monolithic vs. Microkernel OS
• Monolithic OSes have large kernels with a lot of components
• Linux, Windows, Mac
• Microkernels moves as much from the kernel into “user” space
• Small core OS components running at kernel level
• OS Services built from many independent user-level processes
• Communication between modules with message passing
• Benefits:
• Easier to extend a microkernel
• Easier to port OS to new architectures
• More reliable and more secure (less code is running in kernel mode)
• Fault Isolation (parts of kernel protected from other par
• Detriments:
• Performance overhead severe for naïve implementation
97

A microkernel OS
98
Slide adapted from http://web.cecs.pdx.edu/~walpole/class/cs533/fall2015/home.html

Virtual Machines
99
Hardware
OS
Application
Physical Machine

Virtual Machines
100
Hardware
Virtual Machine Monitor (VMM) (aka Hypervisor)
OS
Application
OS
Application
Virtual Machine 1
OS
Application
Virtual Machine 2 Virtual Machine 3

Virtual Machines
101
• Use cases
●Resource configuration
●Running multiple OSes, either the same or different
OSes
●Run existing OS binaries on different architecture

Summary of Lecture set 1
• What is an operating system?
• Operating systems history
• Computer system and operating system structure
102

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